Pressure control valve

ABSTRACT

The present invention relates to a pressure control valve, in particular for electrohydraulic brake systems, including a valve member arranged in a valve housing and a sensor element for determining the fluid pressure that prevails in the valve housing. The fluid pressure in the valve housing is indirectly determined by the sensor element by way of the deformation of the valve housing.

TECHNICAL FIELD

The present invention generally relates to valves and more particularlyrelates to a pressure control valve for use in electrohydraulic brakesystems.

BACKGROUND OF THE INVENTION

WO 00/02755A which was published after the priority date of the presentinvention discloses a pressure control valve of this type which includesa valve member arranged in a valve housing and a sensor element fordetermining the fluid pressure that prevails in the valve housing. Thefluid pressure is determined directly by the arrangement of the sensorelement in the valve housing, to what end corresponding structuralprovisions are necessary which also affect the overall dimensions of thepressure control valve. Due to the relatively high operating pressure, acorrespondingly expensive sensor system is generally required which ispermanently exposed to high pressures.

From generic publication WO 96/33080A a brake system with an electronicbrake pressure control is known which is equipped with an impact soundsensor by means of which the change-over behavior of several pressurecontrol valves of the brake system is established for the approximatedetermination of the brake pressure that prevails in a brake pressuregenerator and/or in several wheel brakes. To this end, the impact soundsensor is respectively arranged at a location of the valve housing of apressure control valve such that the impact sound which is caused when avalve tappet or a valve head gets into contact on the valve housing istransmitted undamped to the impact sound sensor. Consequently, theimpact sound sensor exclusively senses the vibrations which aretransmitted onto the valve housing by the mechanical impulse of themoved valve components.

DE 198 30 464 A1 discloses a pressure control valve of this type whichincludes a valve member arranged in a valve housing and a sensor elementfor determining the fluid pressure that prevails in the valve housing.The fluid pressure is determined directly by the arrangement of thesensor element in the valve housing, to what end correspondingstructural provisions are necessary which also affect the overalldimensions of the pressure control valve. Due to the relatively highoperating pressure, a correspondingly expensive sensor system isgenerally required which is permanently exposed to high pressures.

In view of the above, an object of the present invention is to configurea pressure control valve of the type initially referred to in such a waythat a low-cost determination of the hydraulic pressure that acts in thepressure control valve is ensured by entailing relatively low structuraland functional efforts.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a basic circuit diagram of the sensor assembly that isessential to the present invention.

FIG. 2 shows an embodiment for the design, of a sensor element for theassembly presented in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a simplified view of a pressure control valve 9 which isarranged in a block-shaped valve-accommodating member 14 and isespecially suited for use in electrohydraulic brake systems. Thepressure control valve 9 accommodates in a valve housing 1 a valvemember which is adapted to close or open the pressure fluid channelsdisposed in the valve accommodating member 14 by way of theelectromagnetic actuation of a valve coil 11.

Further, a sensor element 2 is arranged above the valve coil 11 on theoutside of the dome-shaped valve sleeve area. Sensor element 2 is usedto determine the fluid pressure which prevails in the pressure controlvalve 9. According to the present invention, the fluid pressure in thevalve housing 1 is indirectly sensed by the sensor element 2 by way ofthe measurement of the deformation of the valve housing. As regards thedesign of the sensor element 2, it becomes apparent from FIG. 1 that awire strain gauge 5 is fitted to the dome-shaped portion of the valvehousing 1 and, in conjunction with a gauge ring 6 and reference ring 7that will be illustrated in the following in FIG. 2, forms a measuringelement 4 which, by way of exciter ring 8, senses a signalrepresentative of the deformation of the valve housing in the event ofhydraulic pressure variation and transforms it into a pressure signal byway of an appropriate sensing, and evaluating circuit.

According to FIG. 1, the signal-receiving and exciter assembly 3 ismounted directly on a cover 10 which also accommodates the controllingand/or regulating electronics 13 that is required for the operation ofthe pressure control valve 9. Electronics 13 is connected electricallyand also mechanically by way of the electric contacts 12 of the valvecoil 11. Valve coil 11, the controlling and/or regulating electronics13, and the signal-receiving and exciter assembly 3 are thus combined toform a prefabricated assembly in the cover 10. Cover 10 is seated on thevalve-accommodating member 14 that carries the pressure control valve 9.It can be seen in the drawing of FIG. 1 that the sensor element 2 isisolated by an air gap from the signal-receiving and exciter assembly 3so that a non-contact signal transmission occurs between a measuringelement 4, that is integrated in the sensor element 2 and fitted to thepressure control valve 9, and the signal-receiving and exciter assembly3 in which the sensor signal characterizing the valve housingdeformation is transformed into a pressure signal. Therefore, it isproposed for the operation of the sensor element 2 that thesignal-receiving and exciter assembly 3 causes induction of an electricvoltage in a receiving circuit integrated in the sensor element 2, thesaid voltage permitting the operation of the measuring element 4associated with the sensor element 2.

Upon request or requirement, the sensor element 2 and thesignal-receiving and exciter assembly 3 may be provided with acorresponding signal amplifying and/or compensating circuit in order tostabilize the quality of signal transmission.

With a view to ensuring a precisest possible signal determination andsignal transmission with respect to possible air gap tolerances betweenthe sensor element 2 and the signal-receiving and exciter assembly 3, itis disclosed that the sensor element 2 is not only equipped with ameasuring element 4 but with a suitable reference circuit in addition.

A specific embodiment which ensures a stable signal transmission qualityirrespective of the size of the air gap that exists between the valvedome and the cover 10 shall be represented in the following by way ofFIG. 2.

FIG. 2 shows an expedient design of the sensor element 2 which is hintedat in FIG. 1 already. The ;sensor element 2 is shown in a top view onthe valve dome of the valve housing 1. The valve dome represents thearea of the pressure control valve 9 which is sensitive to deformationunder the effect of the hydraulic pressure.

The sensor element 2 which is aligned concentrically to the valve axiscomprises in detail a reference ring 71 and a gauge ring 6 connected toa wire strain gauge 5, the said parts being mounted onto the thin-walledsleeve area of the valve housing 1. Exciter ring 8 is arranged equallycoaxially relative to the sensor element 2 and spaced from the pressurecontrol valve 9 by the air gap. The exciter ring 8 along with thesignal-receiving and exciter assembly 3 forms a construction unit whichis arranged in the cover 10 spaced from the pressure control valve 9. Inthe exciter ring Ii, the signal-receiving and exciter assembly 3 inducesa voltage which is conducted through the reference ring 7 to a certainextent and through the gauge ring 6 to the wire strain gauge 5 toanother extent. The reference ring 7 and the gauge ring 6, in turn,induce magnetic fields which are received by way of the exciter ring 8.The field induction in the exciter ring 8 causes the circulation of analternating current through the ring. Induced current also passesthrough the gauge ring 6 and reference ring 7 so that the thus producedmagnetic fields of the rings 6, 7 can be sensed by means of appropriatesensor elements, for example, by means of Hall elements. Consequently,two sensor signals are available that allow to determine the deformationof the valve housing 1 and, thus, the pressure prevailing in thepressure control valve 9.

An arrangement of this type is suited especially for electrohydraulicbrake systems necessitating a large number of sensor elements 2 whichmay be accommodated between the valve-accommodating member 14 and acover 10 that includes the controlling and regulating electronics 13 andis seated on the valve-accommodating member 14. Another case ofapplication is for traction slip and driving dynamics control systems inautomotive vehicle brake systems.

What is claimed is:
 1. Pressure control valve with integrated pressuresensor, comprising: a valve member arranged in a valve housing, a sensorelement for generating an output signal that is a function of a fluidpressure reaction of the valve housing, wherein the fluid pressurereaction of the valve housing is determined by the sensor element byusing the sensor to detect a deformation of the valve housing, furtherincluding a signal-receiving and exciter assembly and wherein saidsensor element is attached to said valve housing and is wirelesslyconnected to said signal-receiving and exciter assembly, wherein thesignal-receiving and exciter assembly couples an electric signal intosaid sensor element by way of a receiving circuit integrated in thesensor element.
 2. Pressure control valve as claimed in claim 1, whereinthe sensor element or the signal-receiving and exciter assembly includesa compensating circuit to stabilize the signal strength of the outputsignal of the sensor element.
 3. Pressure control valve as claimed inclaim 1, wherein the sensor element includes a gauge element and areference circuit having a reference output signal, and wherein anoutput signal of the gauge element is combined with the reference outputsignal to comprise the sensor element output signal.
 4. Pressure controlvalve as claimed in claim 1, wherein the valve housing includes an areamade from a thin walled sleeve and wherein the sensor element isarranged on said thin-walled sleeve.
 5. Pressure control valve asclaimed in claim 4, wherein the sensor element includes a gauge ring, areference ring, and a wire strain gauge.
 6. Pressure control valve asclaimed in claim 5, further including an exciter ring coaxially alignedwith said gauge ring and said reference ring.
 7. Pressure control valveas claimed in claim 6, further including a cover which accommodates acontrolling or regulating electronics that is required for the operationof the pressure control valve and is electrically and mechanicallyconnected to several electric contacts of a valve coil of the valvemember.
 8. Pressure control valve as claimed in claim 7, wherein thevalve coil, the controlling or regulating electronics, and asignal-receiving and exciter assembly are combined to form aprefabricated subassembly in the cover.
 9. Pressure control valve withintegrated pressure sensor, comprising: a valve member arranged in avalve housing, a sensor element for generating an output signal that isa function of a fluid pressure reaction of the valve housing, whereinthe fluid pressure reaction of the valve housing is determined by thesensor element by using the sensor to detect a deformation of the valvehousing, wherein the sensor element includes a gauge ring, a referencering, and a wire strain gauge.